TM 5-3810-300-24&P-3
1.2.1 Valve Operating Mechanism
5. Loosen the lock nuts at the upper ends of the push
Service
rods, next to the clevises, and unscrew the rocker arms
from the push rods.
Some service operations may be performed on the valve
and injector operating mechanism without removing the
NOTE: If the rocker arms and shafts from two
cylinder head:
or more cylinders are to be removed, tag them
1.
Adjust valve clearance.
so they may be reinstalled in their original
2.
Replace a valve spring.
positions.
3.
Replace or adjust an exhaust valve bridge or
replace a valve bridge guide (four-valve head).
4. Replace a rocker arm.
Inspection
5. Replace a rocker arm shaft or bracket.
6. Replace a fuel injector.
Wash the rocker arms, shaft, brackets and bolts with
It is also possible to replace a push rod, push rod spring,
clean fuel oil. Use a small wire to clean out the drilled oil
the spring seats or a cam follower without removing the
passages in the rocker arms and rocker shaft bolts. Dry
cylinder head. However, these parts are more easily
the parts with compressed air.
changed from the lower side when the cylinder head is
off the engine. Both methods are covered in this section.
Inspect the rocker arm shaft and rocker arm bushings for
wear. A maximum shaft to bushing clearance of .004" is
To replace the exhaust valves, valve guides and valve
allowable with used parts (refer to Section 1.0).
seat inserts, the cylinder head must be removed (refer to
Service replacement bushings must be reamed to size
Section 1.2.2).
after installation.
Remove Rocker Arms and Shaft
The current injector rocker arm used on coach engines
does not use a bushing at the push rod clevis. The bore
area is "lubrited" to provide improved lubrication in this
1. Clean and remove the valve rocker cover.
area.
2. Remove the fuel pipes from the injector and the fuel
connectors.
Inspect the rocker arms for galling or wear on the pallets
CAUTION: Immediately after removing the fuel
(valve or injector contact surfaces). If worn, the
pipes, cover the injector fuel inlet and outlet
openings with shipping caps to prevent dirt or
foreign material from entering.
3. Turn the crankshaft, or crank the engine with the
starting motor, to bring the injector and valve rocker
arms in line horizontally.
CAUTION: Do not bar the crankshaft in a left-
hand direction of rotation with a wrench or barring
tool on the crankshaft bolt, or the bolt may be
loosened.
4. Remove the two bolts which secure the rocker arm
shaft brackets to the cylinder head.
Remove the
brackets and shaft.
CAUTION: When removing the rocker arm shaft,
fold the three rocker arms back just far enough so
the shaft can be removed. Do not force the
Fig. 3 - Removing Push Rod from Upper Side of
rocker arms all the way back with the shaft in
Cylinder Head
place as this may impose a load that could bend
the push rods.
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